If you have made your BuddyPress multilingual by installing it on a multisite WordPress with a different language for each site, you will find that the extended profile field names are available in only one language. Activate this plugin on any of your localized sub-sites (or network activate), go to
Dashboard -> Users -> XProfile Translation
and translate the profile field names and descriptions to your liking. This plugin is BP_ENABLE_MULTIBLOG compatible.